There's an argument to be made that traditional blinding and placebo techniques are not really relevant for interventions targeting mood or personality. e.g. anything that makes you feel better is an effective mood intervention, by definition. "blinding" in these studies is really just going through the motions to make certain authorities happy.
I would be more interested in polling the close friends and family of study participants and asking them about perceived changes. Instruct participants not to tell anyone about their experience in the study (whether they think they got a drug or how much).
It looks like the study tried to do something like this with "session monitors" who interviewed the participants the day after. They call it double-blind, but it's more like single-blind because the 3rd person assessment is the outcome measure.
The issue with relying on placebo effects is not that they aren't real/don't work (everything you said also applies to e.g. a painkiller), but that they are very context-sensitive. Deploy that drug to an individual or population with a different belief framework or contextual information about the therapy or their condition, and you won't get the desired results.
The design you mention is really interesting! Have you seen this done anywhere?
I would be more interested in polling the close friends and family of study participants and asking them about perceived changes. Instruct participants not to tell anyone about their experience in the study (whether they think they got a drug or how much).
It looks like the study tried to do something like this with "session monitors" who interviewed the participants the day after. They call it double-blind, but it's more like single-blind because the 3rd person assessment is the outcome measure.